The present invention relates to high-density recording media, which can be written on and read optically, such as optomagnetic recording media. More specifically, the present invention relates to recording media provided with a resin film and a super-thin coating film, in which a compound including a hydrolysable group, such as a silane compound, is chemically bonded to a substrate surface.
A variety of surface coatings are known conventionally, and typical examples include fluorine resin coatings. Fluorine resin coatings are frequently used as stain-resistant coatings in products that are exposed to water, for example in products related to laundry or cooking, and they are very effective as stain-resistant coatings.
On the other hand, surface modifying agents, such as silane coupling agents, have been used increasingly in recent years, and examples thereof include treatments making the surface of glass stain-resistant and treatments making the surface of glass water-repellent.
Such fluorine resins are sometimes coated on the surface of metal workpieces, but this is very costly. Furthermore, the anti-sticking function when used as a stain-resistant coating may cause a decrease in the adherence to the metal layer below it or decrease its durability due to exfoliation, and the adherence is improved by roughening the layer below or introducing a filler. Therefore, fluorine resin coatings tend to be thick, for example several microns or more. For this reason, fluorine resin coatings may become semi-transparent or non-transparent, and thus cannot be applied to substrates for which transparency is required.
On the other hand, silane coupling agents are used for surface modification of inorganic materials, such as metal surfaces, but they are not suitable for the surface modification of organic materials, so that there are limitations to their use.
In digital video disks (DVD), which are an example of a high high-density recording medium that can be written and read optically, the recording layer is formed on a substrate of polycarbonate. Information is optically written or optically read through a transparent resin layer, and for protection against scratches or the like, the surface of the DVD is covered with a protective layer including a resin film material.
However, this protective layer has the propensity to be easily stained. In high-density recording media, recording errors and reading errors due to staining of the surface are a concern, and as the recording density increases, the effect of such stains becomes large as well. For example, there is the problem that when the high-density recording medium is touched by someone""s finger, oil is transferred from the finger to the recording medium. Also, high-density recording media conventionally are stored in cases, but in future, it can be assumed that they will be removed by hand from the cases for use, like compact disks, and there is accordingly a demand for a countermeasure against staining. In particular, recent DVD disks use blue laser light for high-density recording and reading, so that there is the risk that stains due to fingerprints cause critical defects. Consequently, there is a need for the prevention of stains on optical disk surfaces.
To solve the aforementioned problems, it is an object of the present invention to provide an optical information recording medium, on which a stain-resistant film is formed on the optical disk surface, which is not easily stained, and from which stains can be removed easily, as well as a method for manufacturing the same.
In accordance with the present invention, an optical information recording medium comprises a reflective film, a recording film and a protective film on a substrate,
wherein the protective film is provided in a surface layer on a side opposite to the substrate;
wherein, on an outer layer of at least one selected from the substrate and the protective film, a hard coat resin layer is formed; and
wherein, on an outer layer of the hard coat resin layer, a chemisorptive film comprising organic silane molecules represented by the general formula R4-m-nSiRxe2x80x2mZnxe2x80x94(wherein R is a group including a carbon chain with a carbon number of 3 to 25, Z is O, N or S, n is 1, 2 or 3, Rxe2x80x2 is hydrogen or an alkyl group with a carbon number of 1 to 3, and m is 0, 1 or 2) is formed by covalent bonding with the hard coat layer.
In accordance with the present invention, a method for manufacturing an optical information recording medium comprising a reflective film, a recording film and a protective film on a substrate, wherein the protective film is provided with a surface layer on a side opposite to the substrate, comprises:
spin-coating, onto an outer layer of at least one selected from the substrate and the protective film, an application solution comprising a hard coat resin material, and forming a hard coat resin film by curing it; and
spin-coating a chemisorptive film material comprising an organic silane compound represented by the general formula R4-m-nSiRxe2x80x2mXnxe2x80x94(wherein R is a group including a carbon chain with a carbon number of 3 to 25, X is a halogeno group, an alkoxy group, an isocyanate group or an ester group, n is 1, 2 or 3; n is 1, 2 or 3; Rxe2x80x2 is hydrogen or an alkyl group with a carbon number of 1 to 3; and m is 0, 1 or 2) while the resin film surface is dry; and
causing an elimination reaction between reactive groups of the organic silane compound and active hydrogen of the hard coat resin film surface, so that covalently bonding the organic silane molecules to the hard coat layer.